In the second half of the 20th century the advent of electroencephalography allowed to "look" at the process of dreaming. We finally learned about the different phases of sleep and was able to come close to figuring out their purpose, physiological role.

there are 4 stages of slow sleep and paradoxical phase of sleep. Let's try to deal with them.

How can you learn about the functions and the work of the authority? Method of destruction – damaging the body, and observing the consequences, we can figure out what exactly it is we are "useful". In relation to sleep, this method is, as sleep deprivation for a certain period of time and monitoring changes in your body and behavior.

sleep Deprivation for several days is not provided (despite expectations) to serious and irreversible changes in the psyche or the body of the subjects. Consequences – fatigue, drowsiness, distraction was, of course, unpleasant, but not critical.

people, for obvious reasons, experiments canít last long. Therefore, in his research, the scientists went further in terms of testing on animals. And here it's been a really amazing discovery was that to deprive the body entirely of slow sleep impossible. Experiencing a shortage of this stage, the brain "splits" slow sleep for short periods, and distributes it in some areas. Mechanisms of wakefulness and NREM sleep beginning to work a diffuse and at the same time. Of course, it suffers from the normal behavior – but REM sleep does its work. What kind of work? Today we know about why we need this sleep stage – in the phase of slow sleep is the restoration of homeostasis of brain tissue and to optimize the management of internal organs.

a Completely different picture emerges if the animal is intentionally deprived of paradoxical sleep phase. Eventually chronic inhibition of paradoxical sleep lead to critical consequences (the death of the animal). The immediate cause of death was not discovered. During the experiment rats had discovered a "critical threshold" of a deprivation of a rapid phase – state after which the termination of the experiment had no restorative effect – the animal could no longer sleep and the death was caused during the day. Based on this we can assume that the result was a kind of irreversible damage to the brain.